A 55-year-old diabetic and hypertensive woman presented acutely with vertigo and vomiting. She had right-sided ataxia, horizontal
right gaze-evoked nystagmus, and a right miosis. Later, a right ptosis was noted. Temperature and pinprick sensations on the
right side of the face and left side of the body were disturbed. Examination of the precordium was normal. Computed tomography
of the head showed moderate generalised cerebral atrophy and an old left occipital infarct. There was no evidence of brainstem
or cerebellar haemorrhage.

Six months later the patient presented with excoriation and ulceration affecting the right eyelid, temple and frontal scalp.
She complained of persistent itch in these sites. Swabs from the ulcerated areas were negative, including on viral culture.
She was prescribed …